An off-duty police officer is in a serious but stable condition, after being stabbed in the stomach late on Friday night.
It is believed the 36-year-old was trying to intervene a teenage fight at a Community Hall in Bonnyrigg when the incident occurred.
"Some uninvited guests attempted to gain entry into the hall," Assistant Commissioner Petere Thurtell told Channel Nine.
"As a result of that, some of the people in the hall attempted to speak to the people and an off-duty police officer was stabbed several times in the stomach."
He was taken to Liverpool hospital for surgery, while a 17-year-old boy has been arrested.
Police are appealing for any witnesses with information to contact Crime Stoppers on 1800 333 000.